The present invention relates to a method and apparatus for remotely controlling a device, such as a toy, lock, smart card, or home appliance, via a control message that is imperceptibly embedded In an audio signal, e.g., as a “watermark.” Moreover, the invention optionally enables the device to be synchronized with the audio signal, for example, so that the actions of a doll can be synchronized with a children's television program.
Audio signals are ubiquitous, being broadcast over AM/FM radio, TV, public announcement systems, transmitted over telephone channels, or stored on cassette tapes, CDs, computer memories, etc. Therefore, it is convenient to use audio channels or audio storage to transmit or store some other information.
Audio watermarking, or embedded signaling, has recently emerged as a technology for embedding auxiliary data imperceptibly in a host audio signal. A basic feature of audio watermarking techniques is that the embedded signal is substantially imperceptible to a listener of the host signal. Furthermore, the audio-watermarks occupy the same time/frequency/space domain as the host signal, so that they are not lost in standard audio signal processing, recording or transmissions, nor filtering and/or masking operations in a deliberate attack can remove them.
A primary proposed use of watermarking is in protecting intellectual property rights, e.g., through copy control, automatic broadcast monitoring, ownership dispute resolution, Internet commerce tracking, etc. Alternative applications include auxiliary data embedding, such as the song title and purchasing instructions, assurance of content integrity, proof of performance in TV and radio advertisements, audience exposure monitoring, caller identification (authentication) in telephone conversations, or generic covert communication.
Moreover, various schemes have been proposed for sending command and control signals, or their equivalent, concurrently with audio signals. However, these schemes do not qualify as audio watermarking techniques. For example, in one proposed scheme, an “instructional signal” is inserted in a narrow frequency band set aside at the upper frequency edge of the audio spectrum. However, this system does not qualify as a watermarking system since the host and the control signals occupy distinct frequency bands.
In another proposed scheme, a unique code describing an offer for products and services is transmitted by a TV program as an audible “beep”. There is no attempt to hide this beep, so this technique also is not audio watermarking.
In yet another proposed scheme, information related to a TV game show is encoded in touch tones and broadcast in-band with an audio portion of the show. The touch-tones can be masked by the show's usual sound effects, such as buzzers and beeps. This is substantially different from the watermarking approach, because it cannot simultaneously meet the inaudibility requirement and the requirement for the time domain overlap of a watermark and an arbitrary audio signal.
Accordingly, it would be desirable to provide a watermarking system for sending command and control signals concurrently with audio signals that overcomes the disadvantages of the existing proposed schemes.
The system should use watermarking techniques to provide a hidden data channel in an audio signal for providing short messages, such as device activation commands, or remote control signals that can change the state of a device.
The system should be compatible with existing watermaking techniques, such as those disclosed in U.S. Pat. No. 5,940,135 to Petrovic at al., entitled “Apparatus and Method for Encoding and Decoding Information in Analog Signals,” issued Aug. 17, 1999, and incorporated herein by reference.
The system should provide a hidden remote control signal as a watermark within an audio signal for controlling various devices that detect the hidden signal.
The system should allow the remote control signal to be related to, or independent of, content of the host audio signal. For related content, the system should optionally provide synchronization of the remote control signal with the host audio signal content.
The system should use a watermark to define a time gate (window) during which a device is enabled to receive a user input or perform a specified action.
The system should provide a security mechanism to ensure that the time gate is defined only from a real-time broadcast audio signal, and not from a replay of the audio signal.
The system should improve the robustness and temporal resolution of a watermark, and provide a simplified watermark detector.
The system should provide synchronization of a watermark encoder and decoder.
The present invention provides a system having the above and other advantages.